Thermal Specifications and Design Considerations
Figure 5-6. Processor PECI Topology
Land G5
PECI Host
Controller
Domain 0
5.4.1.1
Key Difference with Legacy Diode-Based Thermal Management
Fan speed control solutions based on PECI uses a TCONTROL value stored in the
processor IA32_TEMPERATURE_TARGET MSR. The TCONTROL MSR uses the same offset
temperature format as PECI though it contains no sign bit. Thermal management
devices should infer the TCONTROL value as negative. Thermal management algorithms
should use the relative temperature value delivered over PECI in conjunction with the
T
CONTROL MSR value to control or optimize fan speeds. Figure 7 shows a conceptual fan
control diagram using PECI temperatures.
The relative temperature value reported over PECI represents the delta below the onset
of thermal control circuit (TCC) activation as indicated by PROCHOT# assertions. As the
temperature approaches TCC activation, the PECI value approaches zero. TCC activates
at a PECI count of zero.
.
Figure 7.
Conceptual Fan Control on PECI-Based Platforms
TCONTROL
Setting
TCC Activation
Temperature
PECI = 0
Max
PECI = -10
Fan Speed
(RPM)
Min
PECI = -20
Temperature
Note: Not intended to depict actual implementation
.
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Dual-Core Intel® Xeon® Processor 3000 Series Datasheet
INTEL [ INTEL ]
